We just watched a great documentary "Nightmares in Red, White and Blue"
http://www.imdb.com/title/tt1337117/ about the history of horror films in America. I was expecting nothing more than a bunch of strung-together clips and it was certainly that, but there was a partly successful attempt to link trends in audience taste to larger socio-political phenomena (e.g., the sexual revolution, vietnam war, nixon, reagan etc), skillfully narrated by Lance Henrikson.